The invention relates to an x-ray diagnostic generator comprising an oil-filled tank in which a high voltage transformer, a high voltage rectifier, and an x-ray tube, connected thereto, are arranged, as well as comprising a circuit arrangement for the formation of an electric signal corresponding to the x-ray tube voltage.
For the formation of a signal corresponding to the x-ray tube voltage which signal e.g. can be introduced as the actual value signal into a control circuit for the x-ray tube voltage, it is known to connect, in parallel with the x-ray tube, a voltage divider and to tap this signal at a resistance of the voltage divider. In addition, it is known to derive this signal from the primary voltage connected to the high voltage transformer, or to tap said signal directly at a tap of the secondary winding of the high voltage transformer. In x-ray diagnosis, medium frequency generators are being utilized to an ever-increasing extent within the feed frequency of the high voltage transformer lies in the kHz-range; i.e. substantially above the mains frequency. In this manner, the high voltage transformer can be provided with a small and lightweight construction. In this instance, the direct tapping of the signal corresponding to the x-ray tube voltage in the primary or secondary circuit of the high voltage transformer does not lead to the required precision. The major reasons for this are the influences of the leakage inductance and stray capacitance as well as the load dependency in the case of utilization of a voltage multiplier circuit as the high voltage rectifier. The factors arguing against the installation of a voltage divider for the purpose of tapping the signal corresponding to the x-ray tube voltage are: the occurring power loss, the space requirement in the tank, the frequency spectrum of the high voltage output (on account of the medium frequency residual ripple, the voltage divider must be frequency-compensated by means of capacitors), as well as the comparatively high costs occurring on account of the requirement of utilizing high voltage precision resistances and high voltage capacitors.